Angle-measurement systems are used to measure rotary motions or rotational positions of a machine part such as a shaft, for example, on which a body having an angle scale is fixated in a rotatably fixed manner. The angle scale may have, for example, an optical or a magnetic graduation which may be scanned accordingly. The rotary motion is measured either incrementally or absolutely, the output measured value being, for example, a sequence of counting pulses, a counter value or a code word. Corresponding angle-measurement systems are used particularly in machine tools on high-speed spindles. Such spindles are increasingly operated at high rotational speeds, for example, up to more than 40,000 revolutions per minute, in order to obtain workpiece surfaces of high quality, e.g., by using cutting machine tools. The mechanical stress on rotating parts that are mounted on such a spindle is accordingly high. In particular, the normally annular bodies having an angle scale, particularly having a magnetic graduation, are connected to the spindles in a rotatably fixed manner such that they are exposed to enormous centrifugal forces. It is a permanent objective to construct bodies having an angle scale that withstand the stresses due to high rotational speeds and which particularly have the required fatigue strength under these stresses. Importantly, these requirements also result from safety-related considerations.
U.S. Pat. No. 4,257,040,for example, describes a body having an angle scale that is attachable in a form-locking manner as a rotating element on a shaft.
Such an arrangement of a rotating body having an angle scale has the disadvantage, however, that its permissible maximum rotational speed is not sufficiently high for high rotational speeds as occur in high-speed machine parts, in particular shafts, or that its fatigue strength is insufficient.